Universal re-encryption of signatures
and controlling anonymous information flow
Marek Klonowski, Miroslaw Kutylowski, Anna Lauks, Filip Zagorski
partially supported by KBN, project 0 T00A 003 23
Anonymous communication protocols, very essential for preserving privacy
of the parties communicating, may lead to severe problems. A malicious
server may use anonymous communication protocols for injecting unwelcome
messages into the system so that their source can be hardly traced. So
anonymity and privacy protection on one side and protection against such
phenomena as spam are so far contradictory goals.
We propose a mechanism that may be used to limit the mentioned side
effects of privacy protection. During the protocol proposed each
encrypted message admitted into the system is signed by a respective
authority. Then, on its route through the network the encrypted message
and the signature are re-encrypted universally. The purpose of universal
re-encryption is to hide the routes of the messages from an observer
monitoring the traffic.
Despite re-encryption, the signature of the authority remains valid.
Depending on a particular application, verification of the signature is
possible either off-line by anybody with the access to the ciphertext
and the signature or requires contacting the authority that has issued
the signature.
Our work is an extension of recent works by Golle, Jakobsson, Juels and
Syverson.